Boiler baffle



Aug. l2,

s. c. SMITH BOILER '-BAFFLE Filed April 4,1928 2 Sheets-Sheet 1 AT TORNEY S. C. SMITH BOILBR BAFFLE Aug. 12, 1930.

`Filed April 4, 1928 2 Sheets-Sheet 2 l NVENTOR l ATroRNEyJ Patented ug.12, 1930 Av,SANFORD C. SMITH, OF HAMBURG, NEW YORK, SSEGNOR TO KINGREFRACTOBIES COMIEANY, ENC., OF BUFFALO, NEVI YORK, A CORE'OBATON OF NEWYORK BOILER BAFFLE Application led April il, 1928. Serial No. 267,208.

This invention relates to bales for boilers and is concernedparticularly with baffles for water-tube boilers of the so-calledhorizontal type. In boilers of this type the hot gaseous products ofcombustion issuing from the grate, fuel nozzles, or the like, arecommonly conducted longitudinally along the boiler tubes by means ofsuitable longitudinal' baffles and then the gases traverse the waterdrum before passing through the flue to the stack. ln another commonform of horizontal boiler the bales are arranged transversely of theboiler tubes so that the Olases are conducted across the tubes inalternate directions along a sinuous path before passing out through thestack. Various other forms of bathe arrangements for horizontal boilershave also been employed but in each arrangement a large proportion ofthe heat of combustion passes out through the flue and is lost becausethe velocity of the gases is greater than the rate of heat transfer orabsorption of the heat by the water in the boiler. This rate of heattransfer is theoretically con'- sidered to be proportional to the squareof `the velocity of the gases, and it is further contended that thisdesirable relatively high velocity of the gases has a scouring effect onthe surfaces of the boiler tubes which removes or prevents the formationof the skin of air or dead gases which is a poor conductor of heat andtherefore diminishes the rate of Y hea-t transfer. However, l have foundthat a greater thermal economy is obtainable in a` boiler when thevelocity of the gases is decreased at certain points in their path, sothat, while the scouring effect on the tubes is not greatly diminished,the gases are in contact with the tubes for a greater period of time,whereby the rate of heat transfer between the gases and the water in thetubes is increased and the temperature of the flue gases is materiallydecreased, and it is the object of this invention to provice means foraccomplishing this purpose.

In accordance with this invention horizontal water tube boilers areprovided with baflles which permit the gases to traverse the boilertubes in part at relatively high veloc 5G ity so that their scouringeffect is utilized,

and permit the gases in part to traverse the tubes at relatively lowvelocity so that the net period of Contact between the hot gases and theboiler tubes is increased and the gas circulation made more thorough,whereby the rate of heat transfer 'between the gases and the water andthe quantity of heat so transferred is increased. T he arrangement ofthe baflles for this purpose consists in placing one baille along thelower rows of tubes from the front to a short distance from the rear ofthe boiler so that the gases enter the bank of tubes at the rea-r, asecond baffle along the upper tubes from the rear to a short distancefrom the front of the boiler, so that the gases may pass from the bankof tubes at the front, and a third or apron baffle extending from thesecond 'baffle at the front of the boiler at an angle so that the gasesare deflected downwardly before leaving the bank of tubes at the front.The angle between the second and third baffles creates a pocket beneaththe second baffle in which a portion of the gases accumulate while othergases pass below the third baille without entering this pocket, but thisangle is made obtuse with respect to the second baille so that the gasesare not trapped in the pocket and damaging explosions cannot occur.lAccordingly, as the gases which accumulate in the pocket cool bytransferring their heat to the water in the adjacent tubes, theirdensity increases so that they fall downwardly in the form of a curtainto be re placed by other hot gases coming from the rear. As thesecooling gases continually fall while transferring their heat to thetubes, they are eventually caught by the current of gases flowing belowthe edge of the 'third baille and carried out to the stack. Auxiliarybaiiles projecting upwardly from the up per baffle and downwardly at theflue may be )rovided in accordance with the type of fuel burned underthe boiler. For example, when burning long-flame anthracite coal underthe boiler, which imparts greater velocity to the gases, other thingsbeing equal, it is advisable to introduce one or more of the auxiliarybaflies described, while the bituminous and lignite coals, thepulverulent, gaseous and liquid fuels and the like, require a diierentarrangement oi these auxiliary baiiles in order to obtain the bestthermal elhciency in the boiler'.

As an alternative or auxiliary installation when low volatile fuelswhose radiant heat is relatively high, such as anthracite. cokebreeze,lignite or the like, are employed, the lowermost baille is spaced fromthe lowest row oi tubes, that is, it is placed along thetllirdibilitli,fifth, VOr other iow Yloiiithe bottom so that these lowertubes are exposed to the radiant heat issuing from the grate. ln orderthat such volatile gases are given oil by the tuel may be ignited beiorepassing outwith the other gases oi combustion, a pocket similar to thatpreviously described is formed under the lower baiile by providing anapron baille extending from the iree rear end oi the lower baille at anangle across the lower tubes into the gas The volatile gases are ignitedwhile in this pocket and are deilected downwardly in the iorm oi acurtain to pass out oi the pocket with the drait below the lower edge oithe apron baille. These hot. deilected gases may be allowed to impingeupon a superheater placed below the lower edge oi the apron baffle.

For a. better understanding` oi the invention, reference is made to theaccompanying drawing in which Figs. 1 and 2 illustrate the arrangementsior horizontal boilers, which constitute this invention. In Fig. 1, aconventional design oi a horizontal water tube boiler is illustrated, inwhich numeral 10 designates the water drum from which depend the irontand rear water legs or headers 11 and 12, respectively. The water tubes13 eX tend between the headers to iorm the bank in the usual manner.This boiler structure is suitably mounted in masonry including iront andrear walls lil and 15, respectively, and a lining oi refractory materialsuch as lire-brick. The stack rises above the ilue 16 at the rear andthe charging and ash doors and the grate 1'? are usually placed beneaththe iront portion oi the boiler, but ii pulverized coal. gas. oil andthe like are used, other constructions are necessary.

Traversing the lower row oi boiler tubes 13 from the iront to within ashort distance oi the rear oi the boiler, leaving passage 18, is lowerbaille 19 which conducts the gases rearwardly into passage 18 andpermits proper combustion oi the fuel gases before they enter the bankoi tubes. An upper baille, 20,

extends along the upper row of tubes from the rear to within a shortdistance of the iront oi the boiler, leaving passage 21. EX- tending atan angle from the iront end 0i upper baille Q0 is an apron baille 22iormed around the boiler tubes which it traverses and consistingpreferably oi initially plastic re The'hot Ygases Voiconibustio'n'pass"irom grate 17 in the direction oi the heavy arrowsthrough passage 18, and into the bank oi tubes across the rear to thetop oi the bank where they are turned forward by the upper baille Q0.The gases then travel longitudi n ally of the tubes, part oi thempassing with relatively h`0'h velocity around the edge oi the apronbaille 52:2, whereby they are conducted across t-he iront portions oithe tubes, through passage 21, and traverse the under surface of waterdrum 10 bei'ore passing to the stack by way oi ilue 16. Tl

.ie remainder oi the gases collect behind apron baille 2.2 in pocket 23.As these gases cool in transierring their heat to tubes around whichthey circulate, their density increases so that they iall downwardly inthe direction oi the dot*- ted vertical arrows in the form oi a curtain,being replaced continuously by hotter gases entering pocket Q3 alongupper baille 20 irom the reir. This curtain oi relatively slowlycirculating gases extends from point located approximately at on theupper baille to the lower edge oi" apron baille 22, this curtain beingdeiined by the phantom line in the drawing which represents theapproximate edge oi the current oi gases which pass di rectly throughthe bank oi tubes and around the edge oi apron baille 22 in the mannerindicated by the heavy arrows. These descend ing gases gradually passinto the gas current to be carried away thereby.

The hot gases which collect in pocket 23 are in contact with the boilertubes about which they circulate ior a suilicient period oi time totransier the greater proportion oi their heat content to the tubes.rl`heir circulation while coniined to the pocket is suilicicntly activeto produce a scouring eilect on the tubes to prevent the formation oithe skin oi dead gases which is a poor conductor oi heat. rlhis is sobecause the velocity oi the hot gases entering the pocket from the rearalong` the under side oi up]A er baille 20 is relatively high andcontinuous in a iorward direction.

The net results oi action ci the curtain oi gases in the pocket behindapron baille 2Q and that oi the current o; gases ilowing under the edgeoi baille Q2 is to retard the flow oi gases as a whole, so that, ingeneral, the area oi the gas passages aiter the gases leave baille :22need not be greater than the area oi the passage around the edge oiballi.. 22, and therefore the area oi iiue 16 need not a., ist

CAD

be greater, thereby effecting a. considerable saving in space, weightand construction costs.

Bepending upon the type of fuel used, auxiliary baille 25 rising abovethe forward end of upper baille 20 at its point of connection with apronbaflie Q2, and auxiliary baflie 26 extending from the flue 16 may beemployed, these auxiliary baffles being shown in phantom in the drawing.rllhe effect of either and both of these auxilia y baflies is thefurther retardation of the flow of the gases, thereby allowing a longerperiod of contact between the gases and the heating surfaces of theboiler. For example, if long-flame or highly volatile fuels areemployed, auxiliary baffle 25 alone may be used in conjunction withbafies 19, 2O and 22 to keep the gases in contact with the bank of tubesfor a longer time, while the gases after passing auxiliary baiiie 25increase in velocity to the i'iue 16. Similarly, if auxiliary baffle 26alone is used in conjunction with bailles 19, 2O and 22, the gases arekept in contact with the bank of tubes and the under side of the waterdrum 10 for a longer time. wWhen employing highly volatile fuels, bothauxiliary baflies 25 and 26 may be used with the combined effects ofthose ascribed to each, namely the retardation of the gases whichpermits them to circulate upon the heating surfaces of the boiler for alonger period of time whereby a greater proportion of their heat isgiven up to the water in the boiler.

1n 2 'an auxiliary or alternative int llation is illustrated. Here thelower bathe 9 does not extend along the lowerinost row tubes, but isspa-ced from the lower tubes as to expose the lowest rows of tubes tothe diant heat issuing from grate 1.7. rThis arngement is particularlyadapted for burnlow volatile fuels, such as anthracite, cokereeze,lignite or the like. Extending at an angle across the lower tubes fromthe free rear end of lower barile 19 is a second apron baille 2?. rhiswhole lower baille, including 19 and 2T, may be used auxiliary to theupper bafhe, 20H22, or may be an alternative arrangement, leaving upperbaffle 2O without the apron 2Q, as in the usual installation.

During operation of the furnace, such volatile gases as are emitted bythe fuel in grate 17, collect in the pocket formed between bafiles 19and 27, and are ignited either by the flame in grate 17 or theincandescence of portions of baffle 19. rl`hese ignited gases are thendeflected downwardly as curtain which slowly descends over thelowerniost tubes, thereby imparting their heat to these tubes. Thiscurtain of gases is then caught by the draft and carried along with theremaining gases below the lower edge of apron baffle 9.0, so as to passthrough passage 18 into the rear end of the bank of tubes. As thesegases are deilected downwardly by the angular apron f5 bafle 27, theymay be employed to impinge upon superheater 28d, of any suitable design,placed below the rear end of the boiler. While a pocket is formedbetween baffles 19 and27, the angularity of baille 27 is such that Aofunburned gases upon opening the draft can occur, wherebythe baffles are.not liable to be blown out or crackedl by explosion, and strain andrupture of the tubes due to this cause is prevented. Inasmuch as thetransfer of heat to the boiler is increased by the new baillearrangement, less heat is lost in the flue gases than heretofore, and ino-ne instance, the temperature of the flue gases has been reduced from750 to 450 F. upon installation of the new baille arrangement. Thisretardation of the flow of the gases also permits more completecombustion so that greater fuel economy isprovided as well as a decreasein the volume and density of the smoke. rllhese and other advantages areobtained by this invention, and although a particular arrangement of thebaffles has been described and illustrated, itis to be understood thatit lies wit-hin the scope ofthe invention to make such altera-tions inthe baflle arrangement as may be necessary to meet the variousconditions of use.

I claim:

1. ln combination with a boiler of the hori zontal tube type, asubstantially horizontal baile extending along the lower tubes from thefront to within a distance of the rear of the boiler so as to leave agas passage into the bank of tubes, a second baffle extending along theupper tubes from the rear to within a distance of the front of theboiler so as to leave a gas passage from the bank of tubes, and a thirdbalile extending at an obtuse angle from the free end ofthe second baleand crossing a portion of the tubes of the bank, the space between theend of the third baffle and the front of the boiler being substantiallyequal to the space between the end of the third baffle and the firstbaffle.

2. In combination with a boiler of the horizontal tube type, asubstantially horizontal baffle extending along the lower tubes from thefrontto within a distance of the rear of the boiler so as to leave a gaspassage into the bank of tubes, a second bafle extending along the uppertubes from the rear to within a distance of the frontof the boiler so asto leave a gas passage from the bank of tubes, a third battle extendingat an obtuse angle from the free end of the second baffle and crossing aportion of the tubes of the bank to form a restricted passage, and a ue,the area of the SGk lll() last-named pa'ssage and the area of the iluebeingIsubstantially equal.

3. n combination with a boiler of the horizontal tube type, vasubstantially horizontal baille extending longitudinally along the uppertubes for the greater part of their length from one end of the boiler,a` second baille extending downwardly from the free end of the lirstbaille across a portion of the tubes, and a third baille extendingupwardly from the opposite side of the first baille approximately at thejunction of the iirst and second bailles.

4. In combination with a boiler of the horizontal tube type, asubstantially horizontal baille extending longitudinally along theuppe'rtubes for thegreater partici their length from one end of theboiler, a second baille extending downwardly from the free end of thefirst baille across a portion of the tubes, a flue, and a third bailleabove the tubes extending downwardly toward the iirst baille and spacedtherefrom, the third baille being arranged in the passage between thesecond baille and the ilue.

5. In combination with a boiler of the horizontal tube type, asubstantially horizontal baille extending longitudinally along the uppertubes for the greater part of their length from one end of the boiler, asecond baille extending downwardly from the free end of the iirst'bailleacross a portion of the tubes, a iluc, a third baille extending upwardlyfrom the opposite side of the iirst bale into the passage between thesecond baille and the flue, and a fourth baille extending downwardlytoward the iirst baille and spaced there-- from, the fourth baille beingarranged between the third baille and the flue.

6. In combination with a boiler having a bank of substantiallyhorizontal tubes, a fire box below the tubes, a ilue, a substantiallyhorizontal baille extending along the lower tubes adjacent the iire boxfrom one end of the boiler to within a distance from the other end, asecond similar, substantially horizontal b'al'eit'ending in theYopposite direction along the upper tubes of the bank, a third bailleextending downwardly from the free end of the second baille into thebank of tubes, a fourth baille extending upwardly from the secondbaille, and a fifth baille extending downwardly toward the second bailleand spaced therefrom, the fourth and fifth baf- '2; iles being arrangedin the passagebetween the third baille and the ilue so as to impart asinuouspatli to the furnace gases.

In testimony whereof l ailix my signature.

SANFORD C. SMITH.

